Erlang（四）顺序程序的错误处理

kailian 2015-05-10

内置函数显示生成错误

  • exit(Why)终止当前进程

  • throw(Why)抛出调用者可能要捕捉的异常

  • error(Why)崩溃性错误

try...catch捕捉异常

try expression of
    pattern when guard ->
        body
catch
    pattern when guard ->
        body
after
    body
end

try...catch具有一个值

fun() [when guard] ->
    body
    try ... end
end



-module(try_test).
-compile(export_all).
generate_exception(1) -> a;
generate_exception(2) -> throw(a);
generate_exception(3) -> exit(a);
generate_exception(4) -> {'EXIT', a};
generate_exception(5) -> error(a).
demo1() ->
    [catcher(I) || I <- [1,2,3,4,5]].

catcher(N) ->
    try generate_exception(N) of
        Val -> {N, normal, Val}
    catch
        throw:X -> {N, caught, thrown, X};
        exit:X  -> {N, caught, exited, X};
        error:X -> {N, caught, error, X}
    end.
demo2() ->
    [{I, (catch generate_exception(I))} || I <- [1,2,3,4,5]].

demo3() ->
    try generate_exception(5)
    catch
       error:X ->
         {X, erlang:get_stacktrace()}
    end.	    
lookup(N) ->
      case(N) of
      1 -> {'EXIT', a};
      2 -> exit(a)
    end.

重点是任其崩溃,永远不要在函数被错误参数调用时返回一个值，而是要抛出一个错误，假定调用者会修复这个错误。

erlang9